Medical procedures involving access to the brain through a burr hole in the skull are used to treat a variety of medical conditions. For example, electrical stimulation of the brain to relieve chronic pain, or for the treatment of movement disorders, may necessitate access via a burr hole. Similarly, burr holes are typically formed to allow implantation of a therapy catheter, e.g., an intraparenchymal (IPA) or intracerebroventricular catheter, to treat various ailments.
Use of a catheter to deliver a therapeutic agent to the brain generally involves the insertion of the catheter into the brain and dispensing the agent at the desired location. During a typical implantation procedure, an incision may be made in the scalp to expose the patient's skull. After forming a burr hole through the skull, the catheter may be inserted into the brain. To accurately place the catheter and avoid unintended injury to the brain, surgeons typically use stereotactic apparatus/procedures. One exemplary stereotactic apparatus is described in U.S. Pat. No. 4,350,159 to Gouda (incorporated herein by reference in its entirety), which may be used to position, for example, an electrode.
As one can appreciate, once an inserted device such as a catheter is properly positioned, it is important that it be adequately immobilized to prevent movement of its distal, therapy delivering tip from its intended location. Even minimal movement of the device tip may reduce therapeutic efficacy of some therapies. Accordingly, reliable methods and apparatus for anchoring and securing the device relative to the burr hole are desirable.
In typical implantations, a free or connecting end of the device (e.g., an IPA therapy catheter) may extend outside of the burr hole and be anchored, relative to the burr hole, with an anchoring device. The free end of the therapy catheter may then be tunneled beneath the skin and connected away from the anchor to a secondary or delivery catheter (e.g., via a connector pin) that is, in turn, coupled to a therapeutic source containing the therapeutic agent. As a result, the agent may be delivered through the delivery catheter and the therapy catheter to the desired location within the patient.
During and after implantation, various forces may act on the delivery catheter. These forces may occur as a result of certain bodily movements (e.g., neck movements, forces transmitted through the scalp, etc.) or from tissue-induced movement (e.g., tissue swelling). These forces may cause the delivery catheter to flex and/or pull relative to the connector pin. Depending on how securely the connector pin is anchored, such forces may ultimately be transmitted to the therapy catheter. If sufficient, these forces may undesirably shift the therapy catheter, and thus its therapy delivery tip, away from the intended location.